1. Field of the Invention
The present invention relates to a vibrating gyroscope suitable for use, for example, in a navigation system which adequately guides a moving object upon detection of the position of the moving object through sensing rotation angular velocity, or in an anti-vibration system such as an anti-shaking device which adequately performs vibration suppression upon detection of rotational angular velocity caused by an externally given vibration such as shaking by a hand.
2. Description of the Related Art
Construction of a conventional vibrating gyroscope will be described with reference to FIGS. 1 and 2. FIG. 1 shows a vibrating gyroscope 21 having a vibrator 2, a mounting substrate 3, supporting pins 4, a supporting plate 5, a circuit board 6, connecting members 7 and buffer members 8.
The vibrator 2 is made of a material capable of performing mechanical vibration such as a permanently elastic metallic material, e.g., elinvar, quartz, glass, ceramics or the like, and has a pillar-like configuration with a regular-triangular cross-section. As will be best seen from FIG. 2, piezoelectric elements 9 and 10 used for driving and detection are attached by, for example, bonding to two adjacent side faces of the vibrator 2. To the remainder of the three faces of the vibrator 2, a piezoelectric element 11 for feedback is attached also by, for example, bonding.
The mounting substrate 3 has a substantially rectangular form having an H-shaped slit 12 which is provided through the substrate 3. The mounting substrate 3 also has four supporting-pin receiving holes 13 formed therein at positions adjacent to the ends of the slit 12, and projection receiving holes 14 located adjacent to both sides of the slit 12.
The vibrator 2 is fixed on the mounting substrate 3 through the intermediary of the supporting pins 4 which are arranged in a pair. Each supporting pin 4 is made of a wire and has a substantially U-shaped configuration. The supporting pins are bonded at mid portions thereof to portions of the vibrator 2 near two nodes of the vibrator 2, with both ends thereof received and fixed in the supporting-pin receiving holes 13. In this state, the vibrator 2 and the piezoelectric elements 9 to 11 are connected by, for example, wire bonding to a wiring (not shown) laid on the mounting substrate 3.
The mounting substrate 3 carrying the vibrator 2 is disposed above the supporting plate 5. The supporting plate 5 has a substantially rectangular form and is provided with a pair of legs 5a at each longitudinal end thereof. The supporting plate 5 also has a pair of projections 5c corresponding to the projection receiving holes 14 formed in the mounting substrate 3 and each continuing from and to a pair of notches 5b. The legs 5a are orthogonally bent downward, while the projections 5c are orthogonally bent upward. The mounting substrate 3 is fixed to the supporting plate 5 so as to oppose the latter across a gap, with the projections 5c received in the projection receiving holes 14.
The circuit board 6 lies beneath the supporting plate 5, through the intermediary of a pair of buffer members 8. The circuit board 6 has an oscillation circuit (not shown) for applying a driving signal to the vibrator 2 and a detecting circuit (not shown) for detecting angular velocity at which the vibrator 2 oscillatorily rotates. Each buffer member 8 is formed from an elastic material such as TEFLON.RTM. polytetrafluoroethylene and has a pillar-like configuration. The buffer members 8 are placed between the respective pairs of legs 5a of the supporting plate 5 and the circuit board 6. The supporting plate 5 and the circuit board 6 are thus fixed together so as to face each other across a gap due to the interposition of the buffer members 8.
A plurality of connecting members 7 are formed by, for example, wire bonding. One end of each connecting member 7 is fixed to the portion of the wiring (not shown) on the mounting substrate 3 at a region near the supporting-pin receiving hole 13, while the other end of the connecting member 7 is connected to a wiring on the circuit board 6, whereby the piezoelectric elements 9 to 11 on the vibrator 2 are electrically connected to the oscillation circuit and the detection circuit.
A driving signal is supplied to the piezoelectric elements 9 and 10 by an oscillation circuit, so that the vibrator 2 vibrates under a bending mode in the direction perpendicular to the surface on which the piezoelectric element 9 is disposed or in the direction perpendicular to the surface on which the piezoelectric element 10 is disposed while the vibration of the vibrator 2 creates two nodes in the vicinity of the portion where the supporting pins 4 holds the vibrator 2. A rotation of the vibrator 2 about an axis 15 causes the direction of the vibration of the vibrator 2 to change to the direction which is perpendicular to the surface on which the piezoelectric element 11 is disposed. The difference between the output voltages from the piezoelectric elements 9 and 10 is detected in this state and based on the value of the difference, the angular velocity of rotation of the vibrator 2 is detected by the detection circuit.
During the vibration under a bending mode of the vibrator 2, the vibration may propagate from one of the two nodes to the other of the nodes via the supporting pins 4 and the mounting substrate 3. Such propagation may interfere with the original vibration of the vibrator 2 and reduce the amplitude of vibration of the vibrator 2. In the vibrating gyroscope 21, however, the slit 12 provides an enlarged path for propagation of vibration, thus suppressing the tendency that the vibration transmitted from the vibrator 2 is propagated from one to the other and vice versa of the pair of supporting pins 4. This eliminates the aforementioned problem of failing to obtain expected amplitude of vibration of the vibrator 2, thus suppressing degradation of performance of the vibrating gyroscope.
The vibrating gyroscope 21 has nevertheless a drawback in that there arises a still possibility to reduce the amplitude of the vibrator 2, which result in degradation of the characteristics of the vibrating gyroscope. According to investigations of the inventors of the present invention, this is because the vibration transmitted from the vibrator 2 to the supporting pin 4 is undesirably propagated to the circuit board 6 through the connecting members 7.
Furthermore, it is necessary to interpose the supporting plate 5 and the buffer members 8 between the mounting substrate 3 and the circuit board 6, requiring an increased number of steps of the assembly process.